It is one of the immutable laws of broadcasting punditry that, the more you protest you know nothing about a subject, the more the researchers and producers become convinced you are just the one for the job. This explains the times I have found myself in front of a microphone talking total bollocks. But fluently, you understand. This is not my problem. It is broadcasting’s problem.

Usually, I get into this pickle by constructing an argument against myself. Not really my bag, I say. I name people who are much more expert. Perhaps producers are so used to turning down people desperate to get on air that they think this is winning self-deprecation. Arguing that you’re the wrong person for the job seems to be a positive aphrodisiac.

Broadcasting does not care if people know anything about a subject or not, so long as they can string a couple of words together. I am adept at this. I know how to top and tail short sentences, and leave pauses between them, to make them easy to edit out of sequence. I’m a soundbite man. Fine, when I know what I’m on about (it happens).

But frankly, if they asked me about the habits of cliff-nesting tern gulls, I could use the same techniques and sound positively authoritative. You just make it up.

Producers don’t listen to the sense, they listen to the rhythm. Occasionally, a slightly puzzled look crosses the face of the presenter questioning you, but it soon passes. His goal is to get to the end of the programme in the allotted time without fluffing his own lines too badly. If all the mouth noises sound about right, it’s a wrap.

But I do less of the microphone-bollocks these days because I have now found a foolproof way to turn down unwanted punditry requests. This is to question the Lewis Carroll logic of broadcasting, the very essence of the medium. It goes like this.

Researcher/ Hi, my name’s Trudi. Is that Hugh Pearman? Great. I’m from London Gobshite Radio and I wondered if you could talk about the new extension to Tate Modern?

Me: Well, as it happens I do know about that. But I’m busy right now. You’d have to do it over the phone.

Researcher (disappointed): Well actually, we were wanting to record it at Tate Modern. Can’t you give up your afternoon to get down there for a 45-second interview for which we shall pay you something insultingly small?

Me: How charming of you to ask. But since this is radio, and since the extension has not yet been built, surely it does not matter if I am at Tate Modern or not. Phones are great, you know. You can hear the words and everything.

Researcher (hurt)/ Oh right. I’ll check with my producer. I’ll get back to you on that.

And doesn’t. Of course not. It wouldn’t be ‘real’ in the radio-Wonderland sense. Result: my afternoon’s work is saved.

Mind you, had they asked, I would have talked about the interesting idea that’s been floated of making the Design Museum a big Tate Modern plug-in at the other end from the wonder-extension. For: it would cash in on those millions of visitors. Against: it would lose its identity in the Tate’s. Worth a few sentences, I’d say. But that’s another immutable law of broadcasting punditry negotiations. Never suggest an alternative topic. It confuses them no end.

So, then: cliff-dwelling tern gulls. They can peer over the edges of their nests, you see, and spot their food right there in the water…